1. Field of Invention
The present invention relates to an electromotive brake system. More particularly, the present invention relates to an electromotive brake system having high reliability of operation by automatically correcting the abrasion of friction pads.
2. Description of Related Art
Generally, an electromotive brake system, different from a typical hydraulic pressure brake, applies pressure to a friction pad by using mechanical mechanism driven by an electric motor and generates braking force.
A conventional electromotive brake system includes a motor rotating to one direction for braking and to the other direction for releasing braking, a screw gear portion connected to a rotation shaft of the motor, and a pressurizing member converting a rotational movement of the screw gear portion into a linear movement and applying pressure to a friction pad.
Since the screw gear portion glidingly contacts to the pressurizing member according to the conventional electromotive brake system, friction loss is great. A ball screw or a roller screw with small friction is used in order to reduce the friction loss. If the ball screw or the roller screw is used, the weight and cost of the system may increase.
In addition, since a lead angle of the screw is constant, applying force of the friction pad to an input torque of the motor is also constant. Therefore, the capacity of the motor should be increased so as to generate large braking force.
Furthermore, the moving distance of the pressurizing member is proportional to the rotation of the motor in the electromotive brake system. Since the maximum rotation speed of the motor is fixed, it takes a certain amount of time for releasing the brake.
Meanwhile, if the abrasion of the friction pad is not corrected when the friction pad of the electromotive brake system is worn out, the brake may not function appropriately even if the motor rotates by a predetermined angle.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.